Exercise $3($convert char digits into int$)$

Write a function that accepts a character array representing digits of an unsigned integer with its digits stored in the reversed order and returns the integer value represented by these characters. For example, the function conver $t$ Int when called on the array char $a[]=\{3^{\text{'}},2^{\text{'}},1^{\text{'}}\}$ would return integer value $123.$ Parameter $n$ holds the number of digits stored in the array.

int convertInt$($char $a[],$ int $n)$